What we know about eating, not eating and overeating has been investigated by research universities and university-trained scientists since the 1920s. The Journal of Nutrition began publishing in 1928. Now 2.5 million inquiries each month probe a massive body of knowledge about the nature of our evolving physical and cultural relationship with food, with at least 30 more food and nutrition journals collecting and dispersing this science globally. 

The result: Americans spend more time debating what to eat than at any other time in history. The firmly held beliefs of most adults about what should be eaten or avoided have origins in the history of...